Retinal detachment is a pathological disorder that occurs when there is a separation of two layers (the neurosensory retina and the retinal pigment epithelium) within the eye that normally remain in apposition. This disorder, if not detected early and treated, results in partial or total blindness. The causes of retinal detachment are myriad.
In a healthy individual, the vitreous gel functions to give shape to the eye, aids in the transmission of light from the lens to the retina, and may provide support to maintain the retina against the underlying retinal pigment epithelial layer. When an individual ages, the vitreous gel may become liquefied at the retina-vitreal layer interface, and subsequently pulls away from the retina with sufficient retinal traction resulting in a retinal break or tear. Continued traction upon the retinal break can result in the passage of vitreous fluid through the retinal break or tear and under the retina, resulting in retinal detachment.
Accepted methods for the treatment of retinal detachments are known in the prior art. Such methods include the removal of the vitreous gel from the eye in an operating room and/or the injection of a gas to seal a retinal break or tear in the upper region of the eye where the gas is used to engage the retina. The gas could only contact the bottom portion of the eye if the patient stood on his or her head. These methods result in sealing a retinal break in order to prevent further retinal detachment. If detachment has occurred, the pressure and surface tension of the gas can hold the retina against the subjacent or underlying tissue and foster a reattachment of the retina to the subjacent tissue. Generally, one of several possible treatment modalities is then used to create a scar between the retinal tear and the underlying tissue to assist in a more permanent reattachment process which progresses with time. These possible modalities include laser photocoagulation, freezing treatment (cryotherapy), diathermy, and microwaves (under investigation). However, none of these retina reattachment procedures, taken alone, incorporate all of the advantages of the various aspects of the present invention to be described.
The use of liquid perfluorocarbons have heretofore been advocated for the treatment of complex retinal detachments. These liquid perfluorocarbons have a low viscosity, high density, and desirable interfacial tension properties which make them ideal compounds for use in treating retinal detachments. The liquid perfluorocarbon materials all share the characteristic of being optically clear and having a higher specific gravity than water, which allows the fluid to hydraulically push the retina back into place and to displace the subretinal fluid anteriorly through preexisting retinal breaks. The low viscosity of these fluids allows for easy injection into the eye and removal from the eye through microsurgical instruments useable outside of an operating room. The liquids are immiscible with water and blood and provide a clear optical pathway during intraoperative bleeding. In addition, their interfacial tension properties prevent the displacement of fluid through small retinal tears into the subretinal space.
U.S. Pat. No. 4,490,351 to Clark, Jr. discloses surgical, operating room methods of treating eye disorders with liquid perfluorocarbons which are either withdrawn immediately during or at the end of the surgical procedure or left in the eye indefinitely. Clark, Jr.'s main use of these liquid perfluorocarbons and substituted derivatives thereof is as fluid substitutes for the vitreous or the aqueous of the eye. Clark, Jr. also recommends the use of liquid perfluorocarbons to transparentize the cornea or lens when either becomes opacified due to degeneration or cataract formation. Clark, Jr. further recommends the use of liquid perfluorocarbon as a method for treating retinal detachments. However, the method used is distinguishable from even the broad aspects of the present invention, as it appears that the vitreous gel is replaced with the liquid perfluorocarbons. This procedure requires the expense of an operating room. It also appears that the perfluorocarbon material is either removed immediately at the end of the operating room procedure or is left as a permanent replacement for the removed vitreous gel. However, in contrast to Clark's disclosure, the permanent use of these materials is believed to cause an undue risk of damage to the eye.
U.S. Pat. No. 5,037,384 to Chang discloses a method and apparatus for the treatment of complicated retinal detachments only, those retinal detachments requiring an operating room. Chang's method uses perfluorocarbon material for hydrokinetic manipulation and as an adjunct to surgical manipulation during vitrectomy. However, Chang discloses a method that involves removing at least a portion of the vitreous gel from the eye and replacing it with an amount of liquid perfluorocarbon sufficient to provide for intraoperative hydrokinetic manipulation of the retina by a surgeon. To avoid what Chang believes to be an undue risk of damage to the eye, the liquid perfluorocarbon is removed at the end of surgery and replaced by a long-term vitreous substitute chosen by a surgeon. Thus, Chang does not consider the use of liquid perfluorocarbons, such as perfluorotri-n-propylamine, the most preferred material of the present invention, for longer term (1-3 or more days) use in the eye.
A preferred specific aspect of the invention is the initial use of a gas in a manner to be described, before use of a transparent liquid or gel retinal reattachment enhancing material. This is in contrast to prior art which has not been applied clinically to human patients, nor applied to retinal detachments. This prior art includes the use of intravitreal gas injections to compress the vitreous gel of the eye of an animal as a preliminary procedure for toxicity tests. This has allowed room for insertion of different materials only to test toxicity within the animal's vitreous cavity and obviate the need for surgical vitrectomy (vitreous removal) in animals.